For words that only have 3 letters, there isn't any 4th letter. As an example with the word “incorporate”, there aren't any a lot more letters Later on and therefore needs to be the word "include". The word “addict” is inside the BIP39 wordlist however, you might have applied “addi” https://userbookmark.com/story19106289/little-known-facts-about-bip39-words